The article “Ultimate Load Capacities of Expansion Anchor Bolts” (J. of Energy Engr., 1993: 139–158) gave the following summary data on shear strength (kip) for a sample of 3/8-in. anchor bolts: . Calculate a lower confidence bound using a confidence level of 90%

for true average shear strength.

n 5 78, x 5 4.25, s 5 1.30 x 1 .67s/ 1n x 2 2.05s/ 1n x 1 .84s/ 1n s 5 3.73 n 5 169 x 5 89.10,